Dazzling DeltaA false color image of one of an ancient river delta at Jezero crater, the newly chosen exploration site for NASA's next Mars rover. The image, which was rendered by Brown researchers, shows the mineralogy of the site, which suggests it may have once been a habitable environment.Credits: NASA/JPL/JHUAPL/MSSS/Brown University

NASA announced this week that the Mars 2020 will look for signs of past life in Jezero crater, a spot that Brown researchers have been studying for more than a decade.

PROVIDENCE, R.I. [Brown University] — After several years of deliberation and input from the science community, NASA has chosen Jezero crater as the landing site for its new Mars rover, which aims to search for signs of past life on the Red Planet. NASA announced the site selection on Nov. 19.

Jezero, an impact crater 45 kilometers in diameter that was home to an ancient lake, is a spot that Brown University researchers have studied for years and championed during the site-selection process. Its star attractions are a pair of preserved deltas, where ancient rivers carried water into a lake thought to have been about the size of Lake Tahoe.

Jim Head, a professor in Brown’s Department of Earth, Environmental and Planetary Sciences, says Jezero is a near-perfect spot to send a rover aimed at looking for evidence of past life. Not only did the crater have an environment conducive to hosting life, it’s also a good spot for preserving ancient biosignatures.

“Jezero was an open-basin lake, which means water flowed in, filled the crater up and then flowed out the other side,” Head said. “The fact that you’re able to fill up this crater — which is quite deep — tells us that the water was there for a substantial amount of time. And then we have these two river deltas in the crater, and we know from Earth that deltas are good repositories for ancient organic matter.”

In 2005, Head and Caleb Fassett, a Brown graduate student at the time who is now a scientist at NASA Marshall Space Flight Center, published the first detailed examination of Jezero and the paleolake and delta deposits. That paper was followed by another study that used orbital observations to show that Jezero had deposits of carbonate and clay minerals. Those minerals, which are widespread in the delta and crater floor, are potential indicators of a once-habitable environment. That work was led by Bethany Ehlmann, another Brown graduate student at the time and who is now on the California Institute of Technology faculty.

Adding to Head and Fassett’s work, Ehlmann’s paper “elevated the science priority of the region immediately,” said Jack Mustard, a Brown professor and Ehlmann’s advisor. “It showed that this site has real astrobiological implications.”

Jezero was an open-basin lake, meaning water flowed into one sideof the crater (right in this image), overtopped the rim and flowed out (left).

From there, another student working with Head and Mustard took up the Jezero mantle. Tim Goudge, a postdoctoral researcher (and soon-to-be assistant professor) at University of Texas Austin, led a 2015 study that detailed the ancient hydrology of the Jezero lake systems, showing that Jezero actually recorded the history of two separate water events on Mars — one event that created the rich mineralogy seen in the delta deposits, and another flooding event that washed those minerals into the crater.

Goudge, working with Mustard and others, helped to lead the charge for Jezero during a series of landing site selection workshops held by NASA starting in 2014. The workshops brought together planetary scientists from all over the world to weigh the pros and cons of various possible sites. They then took a vote to see which sites the science community liked best.

Jezero quickly rose to the top of the bunch, along with another site called Northeast Syrtis that was also championed by Mustard and others from Brown. During each of four separate workshops, Jezero and Northeast Syrtis were consistently neck-and-neck in the voting. They were so popular, in fact, that NASA added a new landing site candidate called Midway — a spot that was between Jezero and Northeast Syrtis, which are located fairly close to each other. The idea was that perhaps the rover could hit both spots.

Ultimately, however, NASA decided that Jezero and its dazzling deltas were the best bet for the rover’s primary mission. There’s still a possibility, however, that the rover could leave Jezero and head for Midway during its extended mission. The Curiosity rover is still rolling around Mars years after its primary mission was completed, and scientists say there’s every reason to think Mars 2020 will do the same.

Mustard said he was impressed with how current and former Brown graduate students influenced the discussion at the landing site workshops. Among those who gave presentations were current graduate students Mike Bramble, Chris Kremer and Jesse Tarnas.

“They put a heck of a lot of effort into this, and they got a lot of attention at the meetings,” Mustard said. “They really had an impact on people’s thinking about where you might want to send this rover.”

Head said that he was pleased to see all the work done at Brown and elsewhere used to help NASA choose a great spot to land a rover.

“It’s been our passion here at Brown to try to piece together the history of Mars — its geology, climate and the possibility that it might have hosted life,” Head said. “When we send missions to Mars, we want to make sure we’re picking the most compelling sites, and we’ve been in that game for a long time.”

The mission is scheduled to launch in July 2020 and land in February 2021.

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